Letter Invaders, based on the now ancient arcade game Space Invaders, is designed to help improve typing skills (and therefore increase your chances of getting some sort of RSI). The idea is to blast aliens out of the sky as they attempt to land on and "kill" you. Since this is a game to improve typing skills, the aliens are words selected randomly from the dictionary. You blast the aliens out of the sky by typing them correctly.
Mac OS X 10.1 or later